WO2021121858A1

WO2021121858A1 - Parabolic trough collector

Info

Publication number: WO2021121858A1
Application number: PCT/EP2020/082839
Authority: WO
Inventors: Ahmed ADEL
Original assignee: Solabolic Gmbh
Priority date: 2019-12-18
Filing date: 2020-11-20
Publication date: 2021-06-24
Also published as: US20220412607A1; AT522960B1; AT522960A4

Abstract

The invention relates to a parabolic trough collector, comprising a parabolic, trough-shaped main reflector (1), a holding device (2), which is preferably in the form of a steel-beam structure and has a plurality of support arms (3, 3') for holding the main reflector (1), an absorber tube (4), which extends along the focal line of the main reflector (1) and in which a heat transfer medium is heated, and a foundation (5), the holding device (2) being mounted on the foundation (5) for rotation about a vertical axis (6).

Description

Paraboir interior collector

The invention relates to an internal paraboir collector. A parabolic inner collector comprises a parabolically shaped mirror channel that concentrates the direct solar radiation on a so-called focal line in which an absorber tube (so-called receiver) is arranged. A medium is passed through the absorber tube, which is heated by the focused solar radiation. The higher the concentration on the focal line, the better the energy yield and the efficiency of the collector. A high energy yield can be achieved in particular through a large aperture of the parabolic mirror.

When increasing the aperture of a parabolic inner collector, however, the problem of increased wind loads occurs, which leads to the parabolic mirror moving or oscillating and focus deviations occurring. Therefore, the aperture of the parabolic mirror is usually small and an elaborate support structure is required in order to avoid focus deviations under wind loads and to maintain optical precision. Conventional paraboir collectors therefore require a large footprint and their aperture is usually limited to around 7.5 m.

In particular from EP 2893268 B1 it is known to provide paraboir inner collectors with a tensioning device, which is designed to tension individual mirror segments, which are arranged on a chain or the like, at a plurality of points of application with a vertical force downwards. As a result, the mirror segments form a parabolic shape without the entire holding structure of the parabolic mirror having to be adapted. Another problem with such parabolic internal collectors is that the wind load increases sharply as soon as the parabolic mirror is rotated about a horizontal axis, for example in order to follow the rising or setting sun. A horizontal rotation causes the collector to reach a height at which the wind load becomes very strong, which causes deformations, so that the size of the collector is limited.

The invention is based inter alia on the object of solving these and other problems of conventional paraboir inner collectors and of creating an improved paraboir inner collector which enables a low wind load with a high energy yield and a high aperture.

This is achieved according to the invention by the features of claim 1.

A parabolic inner collector according to the invention comprises a parabolic, trough-shaped main reflector, a holding device preferably designed as a steel girder construction with a plurality of support arms for holding the main reflector, and an absorber tube which extends along the focal line of the main reflector and in which a heat transfer medium is heated. The holding device is rotatably mounted on a foundation about an essentially vertical axis. The holding device and thus the entire collector are therefore equipped according to the invention with azimuthal tracking.

This has the advantage that the Paraboir inner collector can approximately follow the position of the sun, that is, can follow the sun in a horizontal plane. The azimuthal tracking allows the collector to track the sun in a horizontal plane (horizontal angle) instead of following the sun along its elevation (height angle). A pivoting of the collector, which would lead to a greatly increased wind load, is therefore no longer absolutely necessary; Just by turning it, a greatly increased energy yield can be achieved compared to conventional collectors. Typical dimensions of an internal paraboir collector according to the invention are apertures in the range of 12 m and above with a diameter of the absorber tube of approximately 70 mm. The foundation can be any arrangement that is not necessarily immovable. For example, the foundation can also be a rail arrangement on which the folding device can be moved, or it can be a floating platform. What is essential is the ability of the folding device to rotate relative to the foundation.

According to the invention, several designs are provided in order to achieve a rotatability of the collector about the vertical axis. It can be provided that the folding device comprises at least one, preferably two, particularly preferably three, circular and concentric support circles running concentrically around the vertical axis, preferably made of steel support tubes, in which a large number of rollers, preferably polyamide rollers, attached to the foundation engage . The running surfaces of the rollers point upwards, so that contamination of the running surface and the rollers is prevented.

It can also be provided that a plurality of rollers, preferably polyurethane rollers, are arranged on the folding device itself, which rollers are preferably provided with brushes in order to prevent contamination. The roles can come into direct contact with the foundation. It can also be provided that the rollers engage in circular metallic running grooves specially arranged for this purpose on the foundation in order to achieve better rotatability of the rollers. The rollers are arranged on the folding device preferably point-symmetrically to the vertical axis, for example in a square, a hexagon, or an octagon around the vertical axis. The rollers can also be arranged one inside the other in several shapes, for example a square and an octagon surrounding the square. In this case, two running grooves arranged in concentric circles around the vertical axis can be provided on the foundation.

A plurality of photovoltaic elements for generating electrical energy can be arranged on the folding device. This has the advantage that the photovoltaic elements, like the collector itself, can follow the position of the sun by rotating around the vertical axis. The generated electrical energy can be used to operate a drive motor to carry out the rotation or for other purposes.

The channel-shaped main reflector can extend essentially parallel to the foundation; however, it can also have a preset inclination that is adapted to the expected position of the sun. The inclination of the longitudinal axis of the main reflector with respect to the foundation can be, for example, 5 ° to 45 °.

In order to further increase the energy yield of the Paraboir inner collector and to avoid end losses, it can be provided that a plate-shaped end reflector extending essentially normal to the longitudinal extent of the main reflector is arranged on an end face of the channel-shaped main reflector. The end reflector preferably extends from the apex of the main reflector to two end regions of the main reflector. Furthermore, the end reflector is preferably designed in such a way that it reflects incident sun rays onto the centrally running absorber tube. For this purpose, a slight inclination of the end reflector to the vertical or an inclination of individual elements of the end reflector to the vertical can also be provided. The end reflector can comprise a plurality of plate-shaped mirror elements or the like, which are arranged on a substantially vertically extending carrier. The end reflector reflects the sun's rays, which are reflected beyond the absorber tube, back onto the main reflector at the end of the channel or directly onto the absorber tube, so that end losses are avoided. The azimuthal tracking using the end reflector thus leads to a larger reflective area than is formed by the gross aperture area or collector land area, since part of the solar radiation falls directly onto the end reflector, and then onto the main reflector and subsequently onto the absorber tube or a secondary reflector is reflected.

The absorber tube is arranged centrally along the focal line of the Paraboir inner collector. It can comprise a tubular supply line and a tubular discharge line for the heat transfer medium. The supply line and the discharge line can preferably be routed downward at the end faces of the main reflector in order to prevent the main reflector from being shaded. In order to enable the holding device to be rotated, it can be provided that the supply line and the discharge line in the area of the vertical axis are guided to the outside through an opening in the holding device, preferably in a central recess in the foundation in the area of the vertical axis. This ensures that the supply and discharge of a rotation of the holding device, in particular the rollers of the holding device running on the foundation, do not stand in the way.

In this opening of the holding device, a preferably centrally arranged drive motor, for example a stepping motor, can be arranged for rotating the holding device about the vertical axis. The supply line and the discharge line can be led through a preferably centrally arranged opening in the drive motor, which preferably has a diameter of over 400 mm, particularly preferably over 600 mm, in particular over 670 mm.

The supply line and the discharge line can run upwards or downwards at least in sections along the vertical axis. In order to enable the holding device to be rotated, the supply line and the discharge line can have at least one swivel joint in these sections. As a result, an at least partial rotation of the holding device and the associated supply line and discharge line about the vertical axis is made possible.

However, the supply line and the discharge line can also be routed above the main reflector and do not necessarily have to be routed through an opening in the holding device. In this case the swivel joints are also arranged on the vertical axis, but are located above the main reflector. The swivel joints can be arranged centrally in the area between the main reflector and the absorber tube, or even above the absorber tube.

Alternatively, it can also be provided that the supply line and the discharge line are designed as flexible hoses in the area of the opening of the holding device. In this case, it must be ensured that the flexible hoses can withstand the high temperatures of the heat transfer medium (over 400 ° C). According to the invention, a secondary reflector is provided which runs above and essentially parallel to the absorber tube. The secondary reflector according to the invention serves to direct the rays reflected by the main reflector and possibly also by the end reflector and passing the absorber tube onto the absorber tube by a second (secondary) reflection. This enables larger apertures with the same diameter of the absorber tube, which leads to higher concentrations and fewer thermal losses. The secondary reflector can be formed as an elongated reflective profile, which is polished on its underside, ie the reflection side that is closest to the absorber tube, in order to reflect the incoming light rays like a mirror surface.

The reflective profile can be formed as an aluminum profile or a stainless steel profile, but it can also comprise another reflective material such as glass or a reflective coating. The secondary reflector can be attached to the absorber tube at a certain distance. The secondary reflector can extend over the entire length of the absorber tube.

According to the invention it is provided that the secondary reflector has a circular segment and two straight edge lines in its cross section. This is particularly advantageous if the secondary reflector is designed as a profiled metal sheet, for example an aluminum or stainless steel sheet, which can be bent into the desired shape in a comparatively simple manner. In this case, the circular segment and the two straight edge lines preferably have a highly polished and reflective outer surface. Alternatively, this profile shape can also be formed by joining strips of glass or another reflective material. While the circular section reflects the light rays reflected past the absorber tube directly onto the absorber tube, the straight lines at the edge are designed in such a way that they reflect further primarily reflected light rays passing the absorber tube back onto the main reflector, so that they hit the absorber tube after a further reflection. If necessary, the secondary reflector also reflects the radiation reflected from the edge of the main reflector back onto the absorber tube; this is particularly advantageous if the absorber tube is at the same height as the edge of the main reflector. According to the invention, the circular segment of the secondary reflector can cover an angular range of less than 180 °, preferably approximately 160 ° to 170 °, particularly preferably approximately 165 °. This prevents the reflection of the main reflector from being shaded by the secondary reflector.

According to the invention it can be provided that the circular section of the secondary reflector is arranged above and eccentrically to the longitudinal axis of the absorber tube. This means that the geometric center of the absorber tube and the geometric center of the secondary reflector do not match.

The center of the secondary reflector is therefore preferably well above the center of the absorber tube, particularly preferably by a distance of at least 10 mm. Thus, the cross-sections of the secondary reflector and the absorber tube do not necessarily run concentrically. In embodiments of the invention, the secondary reflector can also be arranged below the absorber tube. This can be particularly advantageous if the ends of the main reflector or the end reflector extend in the vertical direction beyond the vertical position of the absorber tube.

According to the invention, the straight edge of the secondary reflector can extend outward at an angle of approximately 10 ° to the connecting end of the corner points of the circular segment. The straight edge lines preferably have no radial extension in cross section, that is, their extension does not end in the geometric center point of the circular segment. The edge straight lines run more wing-shaped from the end points of the circular segment outwards and slightly upwards.

According to the invention it can be provided that the diameter of the circular segment of the secondary reflector is about three to five times as large as the diameter of the absorber tube, and the straight edge has a length which corresponds approximately to the diameter of the absorber tube. The absorber tube can, for example, have a diameter of approximately 50 mm to 140 mm, preferably approximately 70 mm. However, other dimensions and angles are also provided according to the invention. In particular, the shape and exact dimensions of the secondary reflector can be adapted to the respective application, in particular the shape of the absorber tube and the aperture of the main reflector.

The main reflector can be flexible in shape and can be arranged on a tensioning element suspended between the support arms of the folding device or rest on this. The tensioning element can be a rope, a cable or a chain. In order to force the tensioning element into a parabolic shape even during operation, a large number of spaced-apart points of application are provided on the tensioning element. At these points of application, essentially vertical traction means are provided which can be pulled in the direction of the foundation. The length of the traction means can be adjustable, in particular adjustable by means of turnbuckles or springs. This enables a parabolic shape to be achieved on site without the need for an assembly trap or additional tools. It can react flexibly to wind loads and the tensioning element can easily be returned to its parabolic shape even if it is deformed. When the preload is increased, the resistance to deformation also increases.

According to the invention, the flake reflector can comprise a plurality of essentially identical mirror plates or polished sheet metal plates, in particular aluminum plates, the width of which is preferably in the range of the diameter of the absorber tube, for example approximately 70 mm. The plates can have a flat, that is to say non-curved, reflective surface. The width denotes the extent along the tensioning element. Due to the small width of the plates, a very precise adaptation of the flake reflector to the parabolic shape of the clamping element can take place. However, the length of the plates can be significantly greater. A plurality of plates, for example 7, 10 or 15 plates, can be arranged between two points of application of the tensioning element.

The main reflector can have a multiplicity of main reflector modules, each main reflector module comprising a multiplicity of plates, for example 50, 100, 150 or 200 plates. The holding device can have a plurality of support arms which run parallel to one another, a main reflector module with individual plates being fastened between two parallel support arms.

The main reflector can have a total aperture of more than 7 m, preferably more than 10 m, particularly preferably an aperture in the range of more than 12 m.

According to the invention, it can be provided that the holding device comprises at least one, essentially parallel to the focal line of the main reflector running centrally, inner support strut for holding a maintenance device or other devices. The maintenance device can be supported on the inner support strut during operation.

Preferably, two similar inner support struts are provided, which run parallel to one another over the entire length of the Paraboir inner collector. The support struts are preferably arranged below the absorber tube, that is, they are closer to the main reflector than the absorber tube.

Furthermore, at least one outer support strut can be provided for holding the maintenance device. In particular, an outer support strut running essentially parallel to the focal line of the main reflector can be provided. A particularly stable mounting of the maintenance device can be achieved by suspending it between the inner support struts and the outer support struts. The outer support strut can be part of the holding device or can be connected to the holding device via fastening means.

According to the invention, the inner and / or outer support struts can be designed in such a way that the maintenance device can be displaced along the support struts in the longitudinal direction of the Paraboir inner collector. The maintenance device can be used for the assembly, cleaning and maintenance of the main reflector or individual main reflector modules. This is particularly advantageous in the case of large collectors, where the entire reflector surface can be difficult to reach without a maintenance device. The absorber tube can comprise a multiplicity of sections which are each connected via a flange connection, the flange connection each comprising two end flanges of the sections and a separate adapter piece arranged between them. The adapter piece and the specially designed end flanges enable a modular construction of the absorber pipe on site, even with very long collectors. The adapter piece can comprise an opening for the passage of the heat transfer medium and several, preferably four, circular segment-shaped elongated holes arranged around the opening for the flexible connection of the end flanges to one another. During assembly, the adapter piece is arranged between the end flanges and screwed to them. In order to adapt to end flanges that are possibly slightly rotated relative to one another, the elongated holes preferably each extend over an angular range of approximately 60 ° to approximately 75 °. This means that the sections of the absorber pipe can also be screwed together if they are slightly twisted with respect to one another.

In order to hold the expanded absorber tube, it can also be provided that at least one of the adapter pieces is connected to an absorber tube holder, for example screwed or connected with bolts. Each of the adapter pieces can also be connected to an absorber tube holder. This enables a simple and modular assembly of the absorber pipe on site.

The absorber tube holder can be designed as a vertical support strut that includes a fastening plate at the end. The fastening plate can have elongated holes in which bolts for connection to the adapter pieces are movably guided along the longitudinal axis of the absorber tube. This has the advantage that the absorber tube can thermally expand axially without damaging the construction. In this case, the absorber tube is supported by the absorber tube holder, but remains easily movable axially along the elongated holes in the mounting plate. According to the invention it can be provided that the main reflector comprises a plurality of flexible main reflector modules lined up along the focal line. Such a main reflector module can be designed in the form of several mirror plates or polished metal plates, in particular aluminum plates or the like, which are flexibly attached to one another. The main reflector modules can, however, also be designed in the form of a preferably one-piece, flexible mirror film. The length of the main reflector modules can correspond to half the aperture of the main reflector if, starting from the focal line, two main reflector modules each extend to the support arms of the end regions. The width of the main reflector modules, that is, their extension along the focal line, can be approximately 1.65 m. The width of the mirror plates or metal plates can be approximately in the range of the diameter of the absorber tube, in particular around 70 mm.

The weight distribution of the main reflector modules in the aperture direction (x-direction, normal to the focal line of the main reflector) can preferably be selected such that the main reflector modules, when they hang freely between the support arms of the holding device, assume a parabolic shape due to their weight. In other words, the weight distribution is chosen such that the weight of the main reflector modules per unit length in the x-direction is exactly the same when the main reflector modules assume a parabolic shape. In this case, the tensioning element described above is unnecessary, since the main reflector already assumes a parabolic shape due to its own weight. The traction means described above are also not absolutely necessary, but can nevertheless be used to fix the mirror arrangement.

In particular, it can be provided that the width b (x) of the main reflector modules is not constant along the aperture (x direction), but rather decreases from the focal line to the support arms. In particular, the width of the main reflector modules can follow the following approximation formula:

The value of b (0) denotes the width of the main reflector module in the focal line. The function s (x) denotes the arc length and is used for the parabola

/ (x) = - calculated according to the following formula:

The variable x extends from the focal line of the main reflector (x = 0) to half the aperture of the main reflector, for example x = 6 m for a main reflector with a 12 m aperture.

This ensures that the main reflector modules are the heaviest in the area of the focal line and the lightest in the area of the support arms. As a result, the desired parabolic shape of the main reflector is established by itself solely through the weight distribution. In this embodiment, the main reflector modules are in contact with one another in the area of the focal line, but form gaps in the area of the support arms because they are narrower there.

According to the invention, however, it can also be provided that separate compensation elements are arranged in particular on the underside of the main reflector modules in order to achieve the desired weight distribution. The width of the compensation elements cannot be constant along the aperture, but rather decrease from the focal line to the support arms, so that the compensation elements are heavier in the area of the focal line than in the area of the support arms. In this exemplary embodiment, the main reflector modules are therefore of constant width, so that no gaps arise; the desired weight distribution to achieve the parabolic shape results from the different widths and weights of the compensation elements on the underside of the main reflector modules.

The compensation elements can be made of steel, in particular sheet steel, for example. The compensation elements can be individual plates made of sheet steel, but it can also be a continuous sheet steel. In particular, it can be provided that the width b (x) of the compensating elements decreases in the aperture direction (x coordinate) from the focal line to the support arms. The width of the compensation elements can follow the following approximation formula: 0.001 - s (x)) p _G s _G

The value of b (0) denotes the width of the compensation element in the focal line. The constant p _s is the density of the compensating element, about 7850 kg / m ³ in the case of steel; po is the density of the mirror plate, about 2500 kg / m ³ in the case of glass; s _s the thickness of the compensation element, approx. 1 mm, and SG the thickness of the mirror plate, approx. 4 mm. The function s (x) denotes the arc length and is calculated according to the formula described above.

According to the invention it can also be provided that the Paraboir inner collector has an angle of inclination to the south or to the north, depending on whether it is set up in the southern flemisphere or in the northern flemisphere.

Further features according to the invention emerge from the patent claims, the description of the exemplary embodiments and the figures. The invention is explained in more detail below using a non-exclusive exemplary embodiment in Fland.

Show it:

1 shows a schematic 3-dimensional representation of an exemplary embodiment of a Paraboir internal collector according to the invention;

2 shows a schematic 3-dimensional representation of a folding device of an embodiment of a Paraboir inner collector according to the invention;

3 shows a schematic plan view of the foundation of a further embodiment of a Paraboir internal collector according to the invention;

4 shows a schematic three-dimensional view of the supply and discharge arrangement of an embodiment of a Paraboir internal collector according to the invention;

5 shows a schematic side view of the supply and discharge arrangement of an embodiment of a Paraboir internal collector according to the invention; 6a-6b show a schematic 3-dimensional representation and a cross section through the secondary reflector of an embodiment of a Paraboir inner collector according to the invention;

7a-7b show a schematic 3-dimensional representation and a side view of a flake reflector module of an embodiment of a Paraboir inner collector according to the invention;

8 shows a schematic three-dimensional view of a maintenance device on an embodiment of a Paraboir internal collector according to the invention;

9a-9e show a schematic three-dimensional view of the absorber tube and further views of a flange connection on an embodiment of a Paraboir inner collector according to the invention;

10a-10b show a schematic view of a flake reflector module of a Paraboir internal collector according to the invention.

Fig. 1 shows a schematic 3-dimensional representation of an embodiment of a Paraboir inner collector according to the invention in the entire structure. The parabolic inner collector comprises a parabolic, channel-shaped flake reflector 1, which is composed of several flake reflector modules 34 arranged next to one another. The flake reflector 1 is arranged on a folding device 2 designed as a steel support structure, which comprises a plurality of support arms 3, 3 'for folding the flake reflector. An absorber tube 4, which in the drawing is largely covered by a secondary reflector 15 arranged above, extends along the focal line of the flake reflector 1. A heat transfer medium is pumped through the absorber tube 4, which heats up to temperatures above 400 ° C. during operation due to the reflected sun rays.

Furthermore, a foundation 5 is shown on which the folding device 2 is rotatably mounted about a vertical axis 6 (not shown). A carrier circle 7 is schematically visible under the folding device 2. A feed line 11 and a discharge line 12 are guided through a foundation recess 35 without being in the way of the rotary movement of the folding device 2. Furthermore, photovoltaic elements 9 for generating electrical energy are arranged on the folding device. This schematic illustration also includes a maintenance device 16, which is arranged with two arms on an inner support strut 14 and an outer support strut 28 and carries a non-mounted main reflector module 34.

A plate-shaped end reflector 10 running essentially normal to the longitudinal extent of the main reflector 1 is arranged on an end face of the channel-shaped main reflector 1. The end reflector 10 extends from the apex of the main reflector 1 to the two end regions 26, 26 ‘of the main reflector 1.

The end reflector 10 comprises a multiplicity of essentially identical mirror plates which are arranged adjacent to one another on an essentially vertical support structure.

Fig. 2 shows a schematic representation of a holding device 2 of an embodiment of a Paraboir inner collector according to the invention. The holding device 2 is designed as a steel support structure and comprises eight symmetrically arranged support arms 3, 3 'for holding the main reflector (not shown) 1. On the eight support arms 3, 3' and the eight base struts 36 of the steel support structure, points of engagement 27 are provided in the form of tabs which serve to assemble clamping elements 24 (not shown).

On the underside of the base struts 36 there are rollers 8, which in this exemplary embodiment are designed as polyurethane rollers. The rollers 8 are arranged in two geometric figures around a central opening 13 and vertical axis 6 of the holding device 2, namely an external octagon and an internal square. As a result, a particularly stable support of the holding device 2 on the foundation 5 is achieved.

3 shows a schematic plan view of the foundation 5 of a further embodiment of a Paraboir internal collector according to the invention. In this embodiment, the holding device does not have rollers, but rather the schematically indicated carrier circles 7, 7 ′, which run concentrically around the vertical axis 6. On the foundation 5 rollers 8 are attached, which are directed upwards, and on which the carrier circles 7, 7 'and the holding device 2 itself is rotatably mounted. In this exemplary embodiment, the rollers 8 are designed as polyamide rollers. The supply line 11 (not shown) and the discharge line 12 are led to the outside via a foundation recess 35.

4 shows a schematic three-dimensional view of the supply and discharge arrangement of an embodiment of a Paraboir internal collector according to the invention. The feed line 11 and the discharge line 12 of the heat transfer medium, as well as the opening 13 in the area of the vertical axis 6 of the folding device 2, are shown.

The position of the absorber tube 4 is indicated schematically. In operation, the area above the opening 13, i.e. the absorber pipe 4 and the connected lines, rotates around the vertical axis 6, while the area under the opening 13, i.e. the two parallel supply and discharge lines 12, 13 is stationary. In this exemplary embodiment, the opening 13 has a dimension of approximately 600 mm to 800 mm.

5 shows a schematic side view of the supply and discharge of the heat transfer medium in the area of the opening 13, the vertical axis 6 about which the folding device 2 rotates relative to the foundation 5 is also shown. The tubular feed line 11 and the tubular discharge line 12 each run in short sections in the vertical axis 6. In these sections, swivel joints 17, 18 are provided to allow the holding device 2 and the connected feed line 11 and discharge line 12 to rotate about the vertical axis 6 to enable.

Figs. 6a-6b show a schematic 3-dimensional representation and a cross section through the secondary reflector 15 of an embodiment of a Paraboir inner collector according to the invention. The secondary reflector 15 is designed as an elongated, profiled sheet of aluminum that is highly polished at least on the underside.

In other embodiments, the secondary reflector 15 can comprise other reflective materials. As shown in FIG. 1, the secondary reflector 15 is arranged above the absorber tube 4 in order to direct incorrectly reflected light beams onto the absorber tube in a second or third reflection. The profile of the secondary reflector 15 is shown in detail in FIG. 6b, the position of the absorber tube 4 also being indicated schematically. In cross section transverse to its longitudinal extent, the secondary reflector 15 has a circular segment 19 and two straight edge lines 20. The circular segment 19 covers an angular range of less than 180 °, namely approximately 165 °. The end points 22, 22 'of the circular segment 19 are indicated schematically.

Relative to the absorber tube 4, the circular segment 19 of the secondary reflector 15 is arranged above and eccentrically to the longitudinal axis 21 of the absorber tube 4. Thus, in this exemplary embodiment, the circular segment 19 does not run exactly concentrically to the absorber tube 4, but has a geometric center point which is arranged somewhat above the geometric center point of the absorber tube 4 at a distance.

From the end points 22, 22 ‘of the circular segment 19, the edge straight lines 20 extend outward at an angle of approximately 10 ° to the connecting end of the corner points 22, 22‘. Thus, the edge straight lines 20 do not run radially outward, that is, their geometric extension meets neither the geometric center of the circular segment 19 nor that of the absorber tube 4. This design of the secondary reflector 15 has proven to be particularly efficient.

The diameter of the circular segment 19 is approximately 3.5 times as large as the diameter of the absorber tube 4, and the straight edge lines 20 from the end points 22, 22 ‘have a length which corresponds approximately to the diameter of the absorber tube 4. In the specific exemplary embodiment, the absorber tube 4 has a diameter of approximately 70 mm.

Figs. 7a-7b show a schematic 3-dimensional representation and a side view of a flake reflector module 34 of an embodiment of a Paraboir inner collector according to the invention.

The main reflector 1 is formed by stringing together a large number of such main reflector modules 34. Each main reflector module 34 comprises a multiplicity of essentially similar mirror plates 23, the width of which is approximately in the region of 70 mm. The length of the mirror plates is around 100 cm here; the entire aperture of the main reflector 1, that is to say the direct distance between the end regions 26, 26 'of the main reflector 1, is in the range of approximately 12 m in this exemplary embodiment.

The mirror plates 23 are each flat, that is to say not curved, and are arranged on a tensioning element 24 in the form of a flexible chain. As a result, the main reflector 1 is flexible in its shape. On the clamping element 24, points of application 27 are arranged at regular intervals, which correspond to the points of application on the support arms 3, 3 'or the base struts 36. In order to force the main reflector 1 into a parabolic shape, traction means 25 in the form of struts are arranged at the points of application 27 of the tensioning element 24 and can be tensioned or pulled in the direction of the foundation 5.

In order to mount or dismantle or clean the individual main reflector modules 34 on the holding device 2, inner and outer support struts for a maintenance device 16 are provided in this exemplary embodiment of a paraboir inner collector according to the invention.

8 shows a schematic three-dimensional view of a maintenance device 16 which is suspended between inner support struts 14 and outer support struts 28. In this exemplary embodiment, the inner support struts 14 are part of the holding device 2 (not shown); the outer support struts 28 are fastened to the holding device 2 via brackets 38. The maintenance device 16 can be moved along the inner and outer support struts and carries a main reflector module 34. This figure also shows an elevation 39, which is used to push the maintenance device onto the support struts or to remove it again from the support struts in order to To avoid shadow losses.

9a shows a schematic three-dimensional view of the absorber tube 4. The absorber tube 4 is divided into a plurality of sections 29, which are each connected via a flange connection, the flange connection each comprising two end flanges 30 and an adapter piece 31 arranged between them. FIG. 9b shows the detail A indicated in FIG. 9a in a sectional illustration. The two sections 29 of the absorber tube 4 have end flanges 30 on their faces, which are screwed to one another via an adapter piece 31 arranged between them.

The adapter piece 31 ensures that the end flanges 30 can be tightly connected to one another even with slight play or inaccuracies in assembly. In addition, the adapter piece 31 comprises connecting means 40 which are flexibly connected to an absorber tube holder 37.

Figs. 9c-9d show the adapter piece 31 and the end flange 30 in a schematic plan view. The adapter piece 31 has an opening 32 for the heat transfer medium to pass through and four oblong holes 33 in the shape of a segment of a circle and arranged around the opening 32 for the flexible connection of the end flanges 30. The medium-carrying opening 32 of the end flange 30 is aligned with the opening 32 of the adapter piece 31 arranged in between. The end flange 30 comprises eight circularly arranged bores, which are arranged in such a way that they are essentially covered with the elongated holes 33 of the adapter piece 31. A fixed connection can thus be established even when the end flanges 30 are rotated relative to one another. The elongated holes 33 each extend over an angular range of approximately 75 °. Furthermore, the adapter piece 31 has connecting means 40 in the form of bores for receiving pins or bolts.

9e shows a schematic three-dimensional view of the absorber tube holder 37. This is designed as a vertical support strut and has a fastening plate 41 at the end. The fastening plate 41 has elongated holes 42 which run in the direction of the absorber tube 4. When assembling the absorber tube 4, the adapter pieces 31 can be mounted on the fastening plate 41 via the connecting means 40. The adapter pieces 31 remain movable relative to the fastening plate 41 in the axial direction of the absorber tube 4, for example by inserting bolts or pins into the elongated holes 42 and the connecting means 40. The absorber tube holders 37 thus bear the load of the absorber tube 4, but at the same time allow an axial movement of the absorber tube 4 due to thermal expansion during operation. 10a shows a schematic view of a main reflector module 34 of a Paraboir inner collector according to the invention in plan view. The main reflector module 34 extends in the aperture direction (x-direction) from the schematically illustrated focal line 34 (x = 0) of the Paraboir inner collector to the outside to the support arms (not shown). A second main reflector module 34, not shown, extends outward in the opposite direction. The aperture of the main reflector 1 is approximately 12 m in this exemplary embodiment, so that the main reflector module 34 shown has a length of approximately 6 m.

In this embodiment, the main reflector module 34 is formed by a row of mirror plates 23 of equal thickness, arranged flexibly next to one another. The extent of the mirror plates 23 in the x direction is in each case approximately 70 mm.

The mirror plates 23 are of the same width, but not of the same length, but rather taper outwards from the focal line 34. As a result, the width b (x) of the main reflector module 34 does not run constant along the aperture, but decreases continuously from the focal line 43 to the support arms 3, 3 '. The width b (x) is shown schematically in the left diagram of FIG. 10a. In the area of the focal line, the main reflector module 34 is approximately 1.65 m wide. In the area of the support arms, the main reflector module 34 is approximately 1.2 m wide. When the main reflector modules 34 hang freely between the support arms 3, 3 ', they assume a parabolic shape due to their variable weight distribution. In this embodiment, gaps are formed between the main reflector modules 34 in the area of the support arms 3, 3 ′.

10b shows a schematic view of a main reflector module 34 of a Paraboir inner collector according to the invention in plan view. As in the exemplary embodiment in FIG. 10a, the main reflector module 34 extends in the aperture direction (x direction) from the schematically illustrated focal line 34 (x = 0) of the Paraboir inner collector outward to the support arms 3, 3 '(not shown). In this embodiment, the main reflector module 34 is formed by a row of mirror plates 23 of equal thickness, arranged flexibly next to one another. The extent of the mirror plates 23 in the x direction is in each case approximately 70 mm. In this embodiment, the mirror plates 23 are of the same length, so that no gap is formed, in particular in the area of the support arms 3, 3 '. In order to achieve the desired parabolic shape of the main reflector modules 34, specially cut compensation elements 44 made of sheet steel are arranged on the underside of the main reflector modules 34. The width of the compensation elements 44 is not constant along the aperture, but decreases continuously from the focal line 43 to the support arms 3, 3 '. The width b (x) of the compensating elements 44 is shown schematically in the left-hand diagram of FIG. 10b. In the area of the focal line, the compensating elements 44 are approximately 1.65 m wide. In the area of the support arms 3, 3 ', the compensating elements 44 are approximately 0.5 m wide. When the flaupt reflector modules 34 hang freely between the support arms 3, 3 ', they assume a parabolic shape due to the weight distribution of the compensating elements 44.

The exemplary embodiments according to FIGS. 10a and 10b are based on the materials glass or glass and sheet steel, the density of sheet steel about 7850 kg / m ³ , the density of the glass about 2500 kg / m ³ , the thickness of the sheet steel about 1 mm and the thickness of the glass is about 4 mm.

The invention is not limited to the exemplary embodiments described, but rather includes all Paraboir internal collectors within the scope of the following patent claims.

List of reference symbols

1 main reflector 37 absorber tube holder

2 holding device 38 boom

3, 3 ‘support arm 39 elevation

4 absorber pipe 40 connecting means

5 Foundation 41 mounting plate

6 Vertical axis 42 elongated hole

7, 7 ‘carrier circle 43 focal line

8 roller 44 compensation element

9 photovoltaic element

10 end reflector

11 supply line

12 derivation

13 opening

14, 14 ‘Inner support strut

15 secondary reflector

16 Maintenance device

17 First swivel joint

18 Second swivel joint

19 section of a circle

20 edge straight

21 longitudinal axis

22, 22 ‘corner of the circle segment

23 mirror plate

24 clamping element

25 traction means

26, 26 ‘end area of the main reflector

27 Point of attack

28 Outer support strut

29 Section of the absorber pipe

30 end flange

31 adapter piece

32 opening

33 elongated hole

34 Main reflector module

35 foundation recess

36 base strut

Claims

1. Paraboir inner collector, comprising a parabolic, trough-shaped main reflector (1), a holding device (2) preferably designed as a steel girder construction with a plurality of support arms (3, 3 ') for holding the main reflector (1), an absorber tube (4), which is extends along the focal line of the main reflector (1) and in which a heat transfer medium is heated, and a foundation (5), the holding device (2) being rotatably mounted on the foundation (5) about a vertical axis (6), characterized in that a secondary reflector (15) is provided, which runs essentially parallel to and above or below the absorber tube (4), and is preferably formed by an elongated reflective profile, the secondary reflector (15) in its cross section having a circular segment (19) and two Has marginal straight lines (20).

2. Paraboir inner collector according to claim 1, characterized in that the holding device (2) comprises at least one, preferably two, particularly preferably three, circular and concentrically around the vertical axis (6) extending support circles (7, 7 '), preferably made of steel support tubes , in which a plurality of rollers (8), preferably polyamide rollers, fastened to the foundation (5), engage.

3. Paraboir inner collector according to claim 1, characterized in that a plurality of rollers (8), preferably polyurethane rollers, are arranged on the holding device (2), which are preferably provided with brushes and are preferably arranged point-symmetrically to the vertical axis (6) , for example in a square, a hexagon, and / or an octagon.

4. Paraboir inner collector according to one of claims 1 to 3, characterized in that a plurality of photovoltaic elements (9) for generating electrical energy are arranged on the holding device (2).

5. Paraboir inner collector according to one of claims 1 to 4, characterized in that a plate-shaped end reflector (10) extending essentially normal to the longitudinal extent of the main reflector (1) is arranged on one end face of the channel-shaped main reflector (1) and preferably extends from the The apex extends up to two end regions (26, 26 ') of the main reflector (1).

6. Paraboir inner collector according to one of claims 1 to 5, characterized in that the absorber tube (4) comprises a tubular supply line (11) and a tubular discharge line (12) for the heat transfer medium, which in the area of the vertical axis (6) preferably by a Opening (13) of the holding device (2) are guided or run in the area above the main reflector (1).

7. Paraboir inner collector according to claim 6, characterized in that a preferably central drive motor, for example a stepping motor, is arranged in the opening (13) for rotating the holding device (2) about the vertical axis (6), the supply line (11) and the discharge line (12) are guided through a preferably central round opening in the drive motor, which preferably has a diameter of over 400 mm, particularly preferably over 600 mm, in particular over 670 mm.

8. Paraboir inner collector according to one of claims 1 to 7, characterized in that the absorber tube (4) comprises a tubular feed line (11) and a tubular discharge line (12) for the heat transfer medium, the feed line (11) and the discharge line (12) run at least in sections in the area of the vertical axis (6) and in these sections at least one swivel joint (17, 18) is provided to rotate the holding device (2) and the supply line (11) and discharge line (12) connected to it allow vertical axis (6).

9. Paraboir inner collector according to one of claims 1 to 7, characterized in that the absorber tube (4) comprises a tubular feed line (11) and a tubular discharge line (12) for the heat transfer medium, the feed line (11) and the discharge line (12) are designed at least in sections as flexible hoses in order to enable rotation of the holding device (2) and the supply line (11) and discharge line (12) connected to it about the vertical axis (6).

10. Paraboir inner collector according to one of claims 1 to 9, characterized in that the circular segment (19) covers an angular range of less than 180 °, preferably about 160 ° to 170 °, particularly preferably about 165 °.

11. Paraboir inner collector according to one of claims 1 to 10, characterized in that the circular section (19) of the secondary reflector (15) is arranged above and eccentrically to the longitudinal axis (21) of the absorber tube (4).

12. Paraboir inner collector according to one of claims 1 to 11, characterized in that the edge straight lines (20) extend outwardly at an angle of approximately 10 ° to the connecting end of the corner points (22, 22 ‘) of the circular segment (19).

13. Paraboir inner collector according to one of claims 1 to 12, characterized in that the diameter of the circular section (19) is three to five times as large as the diameter of the absorber tube (4), and the edge straight line (20) have a length that is approximately the Corresponds to the diameter of the absorber tube (4).

14. Paraboir inner collector according to one of claims 1 to 13, characterized in that the absorber tube (4) has a diameter of about 50 mm to 140 mm, preferably about 70 mm.

15. Paraboir inner collector according to one of claims 1 to 14, characterized in that the main reflector (1) is flexible in shape and on a tensioning element (24) arranged hanging between the support arms (3, 3 '), for example a rope, a cable or a chain.

16. Paraboir inner collector according to claim 15, characterized in that the tensioning element (24) can be pulled in the direction of the foundation (5) via a plurality of essentially vertically extending pulling means (25) mounted at spaced points of application (27) to form a parabolic shape .

17. Paraboir inner collector according to one of claims 1 to 16, characterized in that the main reflector (1) comprises a plurality of flexible main reflector modules (34) lined up along the focal line (43).

18. Paraboir inner collector according to claim 17, characterized in that each main reflector module (34) comprises a flexible mirror film or a plurality of essentially similar mirror plates (23) or polished sheet metal plates, in particular aluminum plates, the width of which is preferably in the range of the diameter of the absorber tube (4) , in particular about 70 mm.

19. Paraboir inner collector according to claim 17 or 18, characterized in that the weight distribution of the main reflector modules (34) along the aperture of the main reflector (1) is such that, when it is free between the support arms (3, 3 ') of the holding device (2 ) have a parabolic shape due to their weight distribution.

20. Paraboir inner collector according to claim 19, characterized in that the width of the main reflector modules (34) is not constant along the aperture, but decreases from the focal line (43) to the support arms (3, 3 ‘).

21. Paraboir inner collector according to claim 19, characterized in that compensating elements (44) are arranged in particular on the underside of the main reflector modules (34), the width of which is not constant along the aperture, but rather from the focal line (43) to the support arms (3, 3 ') decreases.

22. Paraboir inner collector according to one of claims 1 to 21, characterized in that the main reflector (1) has an aperture of over 7 m, preferably of over 10 m, particularly preferably an aperture in the range of over 12 m.

23. Paraboir inner collector according to one of claims 1 to 22, characterized in that the holding device (2) has at least one, preferably two similar, essentially parallel to the focal line of the main reflector (1) centrally extending inner support struts (14, 14 ') for holding one Maintenance device (16) comprises.

24. Paraboir inner collector according to claim 23, characterized in that at least one outer support strut (28) is provided for holding the maintenance device (16).

25. Paraboir inner collector according to one of claims 1 to 24, characterized in that the absorber tube (4) comprises a plurality of sections (29) which are connected via a flange connection, the flange connection each having two end flanges (30) and an adapter piece arranged between them (31) includes.

26. Paraboir inner collector according to claim 25, characterized in that the adapter piece (31) has an opening (32) for the passage of the heat transfer medium and several, preferably four, circular segment-shaped elongated holes (33) arranged around the opening (32) for flexible connection of the end flanges ( 30), the elongated holes (33) preferably each extending over an angular range of approximately 60 ° to approximately 75 °.

27. Paraboir inner collector according to claim 26, characterized in that at least one of the adapter pieces (31) is connected to an absorber tube holder (37) to hold the absorber tube (4).

28. Paraboir inner collector according to claim 27, characterized in that the absorber tube holder (37) comprises a fastening plate (41) which is movably connected to the adapter piece (31) via elongated holes (42).

29. Paraboir inner collector according to one of claims 1 to 28, characterized in that the main reflector (1) has a longitudinal axis which is inclined with respect to the surface of the foundation, for example at an angle of approximately 5 ° to 45 °.